A conventional semiconductor element in which a Ga-containing oxide is deposited on an element substrate formed of a β-Ga2O3 single crystal is known (see, e.g., PTL 1).
This type of semiconductor element is formed by laminating a layer(s) of n-type or p-type conductivity on a main surface of a β-Ga2O3 single crystal substrate using a physical vapor-phase growth method such as MBE (Molecular Beam Epitaxy) or a chemical vapor-phase growth method such as CVD.
In addition, a (100) plane having high cleavability and thus providing a flat surface easily is often used as the main surface of the β-Ga2O3 single crystal substrate (see, e.g., PTL 2).